Translations

A sibling is a brother or sister; that is, one
who shares the same parents.

In most societies throughout the world, siblings
usually grow up together and spend a good deal of their childhood
with each other. This genetic and physical closeness may be marked
by the development of strong emotional associations such as
love and enmity. The
sibling bond is often complicated and is influenced by factors such
as parental treatment, birth order,
personality, and
people and experiences outside the family.

Types of siblings

Full sibling

A full sibling (full brother or full sister),
is a sibling that shares both biological or adoptive parents.

Half sibling

A half sibling (half brother or half sister)
is a sibling with one shared biological or adoptive parent. A half sibling that
shares the same mother
(but different fathers)
is known as a uterine sibling, whereas one that shares the same
father is known as an agnate sibling. In law, the term consanguine
is used in place of agnate. Half siblings can have a wide variety
of interpersonal relationships, from a bond as close as any full
siblings, to total strangers. For half siblings in twins, see
semi-identical
twin.

At law (and especially inheritance law) half
siblings were often accorded unequal treatment. Old English
common
law at one time incorporated inequalities into the laws of
intestate
succession, with half siblings taking only half as much
property of their intestate siblings' estates as other siblings of
full-blood. Unequal treatment of this type has been almost wholly
abolished in England and
throughout much of the United
States.

Stepsibling

A stepsibling (stepbrother or stepsister) is a
sibling with whom an individual bears no blood or equivalent
adoptive relation, and is related by the marriage or relationship
of one parent of the individual to one parent of the sibling.

In Islam those who are
fed in this way become siblings to the biological children of their
wetnurse, provided that they are less than two years old and have
been breastfed five times or more by her. Islamic law (shariah) codifies the
relationship between these people, and certain specified relatives,
as rada; once
they are adult, they are mahram, meaning that they are not
allowed to marry each other, and the rules of modesty known as
hijab are relaxed, as with
other family members.

Irish twins

"Irish twins" is a slang term for siblings who are
not actually twins, but
rather, were born less than 12 months apart – possibly in the same
calendar year and/or school year. It references those Irish
Catholic families, on the perception that they have many
children with little space between births. It is sometimes
considered derogatory. Similarly, "Irish triplets" refers to three
siblings born in two years.

Birth order

Birth order is a person's rank by age among his
or her siblings. Typically, researchers classify siblings as
“eldest”, “middle child”, and “youngest” or simply distinguish
between “firstborn” and “later born” children.

Birth order is commonly believed in pop
psychology and popular culture to have a profound and lasting
effect on psychological development and personality. For example,
firstborns are seen as conservative and high achieving, middle
children as natural mediators, and youngest children as charming
and outgoing. In his book Born to Rebel, Frank
Sulloway argues that firstborns to be more conscientious, more
socially dominant, less agreeable, and less open to new ideas
compared to laterborns. Literature
reviews that have examined many studies and attempted to
control for confounding variables tend to find minimal effects for
birth order on personality. In her review of the scientific
literature, Judith
Rich Harris suggests that birth order effects may exist within
the context of the family of origin, but that they are not enduring
aspects of personality.

Some research has found that firstborn children
have slightly higher IQs on average than
later born children. However, other research finds no such
effect.

In practice, systematic birth order research is a
challenge because it is difficult to control for all of the
variables that are statistically related to birth order. For
example, large families are generally lower in socioeconomic status
than small families, so third born children are more likely than
firstborn children to come from poorer families. Spacing of
children, parenting style, and gender are additional variables to
consider.

Regressive behavior at the birth of a new sibling

The
arrival of a new baby is especially stressful for firstborns and
for siblings between 3 and 5 years old. Regressive behavior and
aggressive behavior, such as handling the baby roughly, can also
occur. All of these symptoms are considered to be typical and
developmentally appropriate for children between the ages of 3-5.
While some can be prevented, the remainder can be improved within a
few months. Regressive behavior may include demand for a bottle,
thumb sucking, requests to wear diapers (even if toilet-trained),
or requests to carry a security
blanket.

Regressive behaviors are the child’s way of
demanding the parents’ love and attention. Parents can deal with
these behaviors by explaining to the older child their new sibling
role, making this role sound exciting, answering questions about
the baby and the process of birth (as appropriate), or reserving
time each day just for the parent and older child.

The AAP (American Academy of Pediatrics http://aap.org) suggests that instead of
protesting or telling children to act their age, parents should
simply grant their requests without becoming upset. The affected
children will soon return to their normal routine when they realize
that they now have just as important a place in the family as the
new sibling. Most of the behaviors can be improved within a few
months.

The University of Michigan Health System http://www.med.umich.edu/ advises
that most occurrences of regressive behavior are mild and to be
expected; however, it recommends parents to contact a pediatrician
or child psychologist if the older child tries to hurt the baby, if
regressive behavior does not improve within 2 or 3 months, or if
the parents have other questions or concerns.

Sibling rivalry

Sibling rivalry is a type of competition or
animosity among brothers and sisters. It appears to be particularly
intense when children are very close in age and of the same gender.
Sibling rivalry can involve aggression; however, it is
not the same as sibling
abuse where one child victimizes another.

Sibling rivalry usually starts right after, or
before, the arrival of the second child. While siblings will still
love each other, it is not uncommon for them to bicker and be
malicious to each other. Children are sensitive from the age of one
year to differences in parental treatment and by three years they
have a sophisticated grasp of family rules and can evaluate
themselves in relation to their siblings. One study found that the
age group 10 to 15 reported the highest level of competition
between siblings Sibling rivalry can continue into adulthood and
sibling relationships can change dramatically over the years.
Approximately one-third of adults describe their relationship with
siblings as rivalrous or distant. However, rivalry often lessens
over time and at least 80 percent of siblings over age 60 enjoy
close ties. Evolutionary
psychologists explain sibling rivalry in terms of parental
investment and kin
selection: a parent is inclined to spread resources equally
among all children in the family, but a child wants most of the
resources for him or herself.

The opposite phenomenon, when relatives do fall
in love, is known as genetic
sexual attraction. This can occur between siblings brought up
apart from each other, for example, adoptees who are re-united in
adulthood.